Two methods used to theoretically hinder the evolution of antibiotic resistance proved ineffective in a new study published in the journal of Molecular Biology and Evolution.

For the study, clinical scientists and mathematicians reviewed accumulated data on clinical trials to determine the efficacy of mixing — a random assignment of appropriate-class antibiotics — and cycling — a process akin to crop rotation in which certain antibiotics are withheld for a period of time.

Analysis of the data, which amounted to more than 4 million patient days of treatment, showed no significant correlation between the prevention strategies and the prevalence of antibiotic resistance.

"For example, in the doomsday scenario that multi-drug resistance is endemic and present in every infection before the patient begins treatment, it matters little which treatment patients are given," said study co-author Rafael Pena-Miller, PhD, an assistant professor in microbial systems biology at UNAM Morelos in Mexico. "But before that stark situation arises, targeting appropriate treatment at as many individuals as possible outperforms both mixing and cycling."